7TH INTERNATIONAL CONGRESS ON TECHNOLOGY - ENGINEERING & SCIENCE - Kuala Lumpur - Malaysia (2019-08-08)

Heat Transfer Augmentation and Energy Savings using Compound Enhancement Technique for Thermal Systems
The use of various enhancement techniques to augment convective heat transfer coefficient inside tubes has been investigated for many years. The high cost of energy and material has resulted in an increased research for producing more efficient heat exchange equipment [1]. The heat transfer augmentation is a subject of vital importance in increasing the heat transfer rate and achieving higher energy efficiency in thermal management. The heat transfer augmentation techniques are classified into passive, active and compound techniques [2]. The interesting features of the inserts and their promising potential in many heat transfer applications such as heat exchangers, nuclear reactors, solar heaters, gas turbines and combustion chambers have prompted different studies [3]. In the present experiment, the wire coil insert and screw tape have been used together in order to enhance heat transfer characteristics. The effect of tooth horizontal length of the screw tape has been presented in this study. Laminar flow of the working fluid was considered with Reynolds number ranging between 100 -800. The experiment has been carried out in a brass channel and friction, momentum, pressure and drag loss tests have been carried out in an acrylic channel. A hydrodynamic development opportunity was given to the fluid by a sufficient length of the channel before the fluid entered the inlet section of the heated channel. Thus a hydrodynamically fully developed flow was established before the thermal entrance length was encountered by the fluid. The channel was heated by the nichrome wire through which electric current (of low Ampere) passed at different voltages maintained in the system by using autotransformers. The outside wall temperatures at different axial and peripheral locations were measured by using copper-constantan thermocouples. The thermo-emf was measured by using digital multimeter. The fluid bulk mean temperature at inlet and outlet were also measured by thermocouples. The intermediate bulk mean temperatures of the fluid were interpolated. The test-section was well insulated thermally. Figure 1 and Figure 2 show the impact of variation of tooth horizontal length on friction factor and Nusselt number. The tooth horizontal length was varied for dstar= 0.0625, oblique teeth angle = 45o; helix angle =60o, aspect ratio = 1.0. The friction factor was noted to be increasing with Reynolds number. The friction factor was also observed to be increasing with tooth horizontal length. Similar trend was observed for Nusselt number. Nu increased with both Reynolds number and tooth horizontal length. The maximum and minimum were recorded at horizontal tooth length of 0.0625 and 0.1538, respectively for both friction factor and Nusselt number.
Miss Madhu Sruthi Emani, Mr. Hrishiraj Ranjan, Mr. Anand Kumar Bharti, Professor Sujoy Kumar Saha